Surgical procedures often require a surgeon to gain access to a cavity in a patient's body. Generally, when such a procedure is required, an incision is made in an exterior wall of the cavity and an instrument is inserted into the working channel created by the incision. One common instrument used in such a procedure is a trocar assembly. Trocar assemblies include a variety of components, but generally can include a trocar cannula, a trocar obturator, and a trocar housing. In many designs, in order to access the body cavity, the trocar cannula is directed through the skin and the trocar obturator is inserted through an interior lumen defined by the cannula. The trocar obturator is then used to penetrate the skin, which has often already had an incision made in it with a scalpel or similar device, and access the body cavity. More specifically, in some designs, applying pressure against a proximal end of the trocar obturator allows a sharp point at a distal end of the trocar obturator to be forced through the skin until it enters the body cavity. Then, the trocar cannula is inserted through the perforation made by the trocar obturator and the trocar obturator is withdrawn, leaving the inner lumen of the trocar cannula as a path to access the body cavity from outside of the body.
The trocar housing can be joined to a proximal end portion of the trocar cannula, and further, the housing can define a working chamber with an open distal end portion that is in communication with the interior lumen of the cannula. Just as the interior lumen can receive the obturator, it can also receive other elongated surgical instruments such that the instruments can be axially extended into and withdrawn from the cannula through the proximal end portion of the working chamber defined by the trocar housing. For example, in order to allow a surgeon to more easily see during a procedure, an endoscope can be inserted through the cannula and proximal or into the body cavity.
It is common for a sealing assembly or sealing device to be used in the trocar assembly. Sealing assemblies and devices are often generally referred to as valves. Sealing assemblies generally help prevent fluid or gas from escaping during surgical procedures. Such prevention is needed, especially during certain minimally invasive surgical procedures, in which an insufflation gas is used to expand a body cavity. However, it can be difficult to maintain the internal gas pressure because during the course of the procedure instruments are typically passed into and out of the trocar assembly. Accordingly, a sealing assembly, and often two sealing assemblies, are generally provided in the trocar assembly. The sealing assembly can seal against an outer surface of inserted instruments and thus can prevent fluids and insufflation gas from leaving and/or entering the body cavity through the trocar cannula.
In instances where two sealing assemblies are provided, the one that is a top, or proximal, seal is usually designed to seal around a surgical instrument when it is present, and the bottom, or distal, seal is usually designed for sealing the trocar cannula when the instrument is not present. One type of distal seal is a “duckbill” seal, which is sometimes referred to as a zero-closure valve. A duckbill seal assembly generally includes a pair of opposed valve members which open and close a seal face in much the same manner a duck opens and closes its bill. The opening and closing of the duckbill seal assembly can generally result from the insertion and/or removal of an instrument from the duckbill seal assembly. More specifically, the duckbill seal assembly can generally be opened by contacting an inner surface of the seal face with the instrument. Further, the valve members can include a straight wall angle which defines a flex point for the opening and closing of the assembly, or alternatively, they can include multi-angled walls that can serve the same purpose but that can also have improved tear resistance and buckling prevention. Some examples of such valve members can be found in United States Publication No. 2005/0077688 of Voegele et al., filed on Sep. 17, 2004, and entitled “Multi-Angled Duckbill Seal Assembly,” which is hereby incorporated by reference in its entirety. An inner surface of each of the valve members and the seal face is generally in contact with an environment outside of the body cavity while an outer surface of each of the valve members and the seal face is generally in contact with an environment inside of the body cavity.
While such sealing assemblies are effective to prevent fluids and insufflation gas from leaving and/or entering the body cavity through the trocar cannula, fluid from both outside and inside the body cavity often builds up on both the inner and outer surfaces of the seal face, respectively. Thus, as instruments are passed through the sealing assemblies and come into contact with the seal face, fluid that exists on the inner and outer surfaces of the seal face is often wiped directly onto the instruments during the course of a procedure. This is especially problematic for instruments such as endoscopes and laparoscopes because fluid is often wiped directly onto the camera lens and thus obscures the surgeon's view.
Accordingly, there is a need for a seal assembly that reduces the amount of contact between instruments being passed into and out of the seal assembly and a seal face of such seal assembly.